Continuous biochemical monitoring has the power to change currently accepted standards of care, shifting the emphasis from treating illness to maintaining health. Point-in-time snapshots of a patient's health can miss critical fluctuations or early warning signs that might warrant early interventions or changes in disease treatment and management. PROFUSA's sensor platform has the promise to transform healthcare by providing real-time data to physicians and patients without requiring blood samples, cumbersome equipment, or doctor visits. The goal of this Fast Track STTR is to apply PROFUSA's injectable microsensors for monitoring tissue health in peripheral artery disease (PAD). Continuous oxygen monitoring will be useful in the treatment and management of a variety of diseases, such as asthma, COPD, sleep apnea, compartment syndrome, transplant surgery, and PAD. PAD is a manifestation of systemic atherosclerosis that affects 8-12 million people in the U.S., with prevalence increasing with age. PAD ranges from mild (accompanied by intermittent claudication or pain with exercise) to severe (accompanied by critical limb ischemia and gangrene), and is associated with high rates of amputation, mortality and poor quality of life. With the appropriate treatment and monitoring, disease progression can be halted and even reversed. PROFUSA's long-term tissue monitors can be used to continuously monitor tissue oxygen levels and temperature in PAD patients during their daily activities and thus provide timely indications of changes in disease state (e.g. restenosis). In recently completed landmark studies, PROFUSA's prototype oxygen sensors were shown to function 13 months in healthy rats and 3 months in large, healthy mammals. In this Fast Track STTR, we propose to demonstrate sensor functionality in PAD animal models: rats in Phase I and pigs in Phase II. Changes in tissue oxygen in the animals' healthy and ischemic legs will be monitored before, during, and after induction of PAD out to 90 days, a time period relevant to chronic wound healing, thrombolytic drug therapy optimization and monitoring for restenosis to avoid re-intervention and amputation. Phase II will also involve miniaturization of PROFUSA's custom optical reader system to improve the form factor for in vivo use. In addition to the strong scientific and pre-clinical team, medical, clinical, regulatory and business personnel will be an integral part of this project to provide early strategy for successful product development. The proposed studies will provide valuable data for advancing PROFUSA towards clinical studies of PAD monitoring and significant investor funding to enable commercialization for widespread clinical application.